The various forms of the HIV-1 envelope (Env) glycoproteins do not serve as ideal immunogens because they poorly induce Abs (Abs) with broad anti-viral functions, and the Ab response lasts <6 months. To overcome these limitations, epitope-scaffold immunogens can be used to focus the Ab response on vulnerable sites on the Env; however, the design of HIV epitope-scaffold immunogens has been fraught with many failures. Nevertheless, epitope-scaffold vaccines candidates have been successfully developed against influenza and Neisseria, and we and others have succeeded in designing several V3-scaffold and V3 peptide immunogens with demonstrable antigenicity and immunogenicity, resulting in the induction of HIV-1 cross-clade neutralizing Abs. In this Project, we propose to focus the immune response on the V2 region of gpl 20. Until recently, this region was virtually overlooked as a target for vaccine development, but its importance as a vaccine target has been recently supported by data showing that anti-V2 Abs can be highly cross-reactive, display neutralizing activity, capture virus particles, and block gp120/a4p7 interaction. Support for pursuing V2 as a promising antigen for vaccine design also comes from pilot studies with specimens from the RV144 clinical vaccine trial. For this Project, we will apply the platform we developed for generating V3-scaffold immunogens to the production of V2-scaffold immunogens to be used for boosting the Ab response after priming with DNA Env. For Aim 1.1, we will construct V2 inserts for scaffolded immunogens based on the fine specificity of human V2 polyclonal and monoclonal Abs (mAbs), and on bioinformatics and molecular modeling data. In Aim 1.2, we will assess the prevalence and function of anti- V2 Abs of different specificities and clarify how these differ relative to the infecting HIV clade. For Aim 1.3, we will select and characterize new human V2-specific mAbs derived from non-clade B-infected donors from Cameroon infected with the clades that induce the most broad and functional anti-V2 Abs. Finally, after selecting V2-scaffold proteins which, from the results of Aim 1.2 and 1.3, react with the most broad, potent and multifunctional anti-V2 polyclonal and mAbs, we will, in Aim 1.4, test the immunogenicity of selected V2 scaffold boosting immunogens in rabbits and non-human primates after priming with Env DNA. The ultimate goal of this Project is to induce antl-V2 Abs in rabbits and non-human primates that display cross-clade anti-viral activities that mediate protection.